The consistency between measurements of the femoral neck anteversion angle in DDH on three-dimensional CT and MRI.

Abstract

Three-dimensional computed tomography (3D CT) has been regarded by some investigators as the gold standard for measurements of the femoral neck anteversion angle (FNA) in developmental dysplasia of the hip (DDH), although a simple and reliable imaging method using a non-ionizing technique is needed. To determine the consistency between measurements of the FNA in DDH using 3D CT and magnetic resonance imaging (MRI) and to estimate the precision, reliability, and reproducibility of MRI for the measurement of the FNA and assess whether MRI could replace 3D CT. 3D CT and MRI were used to measure the FNA in 22 patients, including 18 girls and four boys, with a mean age of 3 years (age range, 1-7 years). All of the measurements were performed independently by two radiologists at different times. This exercise was repeated 2 weeks later by one of the radiologists. High consistency was found between the MRI and 3D CT measurements (intraclass correlation coefficient [ICC] of 0.906, P < 0.05). The mean inter-observer and intra-observer agreements were high for MRI (ICC = 0.948 and 0.964, respectively, P < 0.05 for both) and for 3D CT (ICC = 0.942 and 0.966, respectively, P < 0.05 for both). Compared with 3D CT, MRI provided a precise, reliable and reproducible method of measuring the FNA in DDH. MRI is recommended as an appropriate technique for measurement of the FNA in DDH, and this approach could replace 3D CT because it delivers no ionizing radiation and offers a better display of soft tissue pathological changes.